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Re: [EGCS] Optimizations
- To: ronis at onsager dot chem dot mcgill dot ca
- Subject: Re: [EGCS] Optimizations
- From: Marc Lehmann <pcg at goof dot com>
- Date: Wed, 10 Dec 1997 18:46:33 +0100
- Cc: egcs at cygnus dot com
- References: <199712091751.MAA18879@ronispc.chem.mcgill.ca>
- Reply-To: egcs at cygnus dot com
> gcc -O6 -mpentium -fomit-frame-pointer -fexpensive-optimizations \
> >-ffast-math
>
> To that, add:
> -march=pentium
> -fschedule-insns
> -fschedule-insns2
> -fregmove
> -fdelayed-branch
>
> According to the gcc info description, all the -f options are enabled
> (if supported) when -O2 (and I presume -O6) is specified. Is this
> correct?
no, you misread the info files. almost everything
except -finline-functions and -fomit-frame-pointer is enabled at -O2,
-O3 enables -finline-functions.
-fschedule-insns is a *loss* on x86 cpu's!
> -malign-double -malign-loops=0 -malign-jumps=0 -malign-functions=0\
> -mno-ieee-fp
>
> Are the -malign directives implied by -march=pentium? (they probably
on pgcc, yes, on egcs, no. the mno-ieee-fp is a bit buggy.
the -mpentium should be selected automatically when you compile
for i586-*-*, but I'm not exactly sure here.
> Is -mno-ieee-fp implied by -ffast-math?
no.
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